This application claims the benefit of International Application Number PCT/SE00/01553, which was published in English.
The present invention refers to a combined domestic machine for washing and drying textiles, comprising a wash liquor tub which contains an inner drum rotatably provided and supporting the textiles during the washing and drying processes and having a volume adapted to requirements relating to the wash process, water supply means for supplying water into the tub, water draining means for draining washing and rinsing liquid from the tub, means for driving a moisture absorbing gaseous medium through the inner drum, and program control means for controlling the washing and drying processes. The invention also relates to a method for washing and drying textiles in a treatment chamber, wherein the textiles are first treated in a conventional water washing process, dewatered by means of spin-drying and then dried by means of superheated steam circulated in a closed loop past the textiles.
Combined machines for washing and drying textiles are known, e.g. from patent publication GB-A-2181220. Such machines have been provided as an option for a completely automatized washing and drying process for articles of clothing. Another object is to reduce the space required in order to provide for both washing and drying of articles of clothing in a room.
Domestic laundry washing machines of today have been optimized as to the functions of washing and spin-drying and have a given drum volume such that the machine can handle wash loads of 4-5 kilos of dry laundry. Drying of the same wash load by means of tumbling in a drying drum calls for essentially double the drum volume. Accordingly, the traditional solution has been to provide a washing machine and a tumble drier each optimized for its respective task.
For the purpose of reducing space solutions have also been offered where the tumble drier has been mounted on top of the washing machine in a secure way. Thereby, to some extent the problem of space has been solved, however, the automated washing and drying process is still waiting for its solution.
When drying garments in a washing drum with circulating hot air the drum volume must have a fair size in order for an even drying to be achieved and the garments not to get creased. As a result, if the full capacity of the machine in the washing process is used the subsequent drying has to be carried out in two batches, each comprising half the wash load. Accordingly, there is a desire for rendering the drying process more effective so that the whole wash load can be tumbled in one go without the process taking a disproportionately long time and without the laundry garments getting creased in an unallowable way.
It has now been found that replacing the hot air with superheated steam causes the heat transfer to the fibres of the garments to take place more efficiently at the same time as the tendency of creasing is reduced.
Patent publication EP-A-101074 discloses such way of using superheated steam in drying laundry in a tumble drier or the like. The drying process comprises two phases where in a first phase as fast as possible the laundry is heated to a temperature of 99-100xc2x0 C. The heating is achieved by the supply of wet steam. In a subsequent second phase the steam is led through a heat exchanger to be superheated and is then circulated past the laundry to remove the moisture remaining in the laundry.
The publication EP-A-395685 also describes the use of superheated steam for drying of laundry.
In the publication EP-A-101074, referred to above, a heat exchanger is used for heating the steam to become superheated. In patent publication FR 2496781 a drying apparatus for products such as corn, fruit, wood and the like is described, wherein steam emitted from the products during the drying process is led to a compressor to be compressed and then led to a condenser which returns heat to the products for the evaporation of additional moisture. The products are heated by means of superheated steam circulated by means of a fan past the products and heated by the condenser. By use of the steam compressing system a very high thermal efficiency is achieved. As a matter of fact: 3-4 times as much water is extracted per unit of supplied energy as compared to previous drying systems.
Based on the prior art technique described it is an object of the invention, in particular in combined domestic machines for washing and drying of laundry, to further improve the efficiency of the drying process described in the publication EP-A-101074 by application of the technique described in the publication FR 2496781. The object is achieved in a combined machine for washing and drying textiles, where dry superheated steam is circulated in a closed loop past the textiles, and compressor means is provided to compress part of the steam and lead it to a heat exchanger means. The heat exchanger means condenses the compressed steam and returns the heat released during the condensing process to the steam in the closed loop. The objective is also achieved by a method for washing and drying textiles in a treatment chamber, where the textiles are first treated in a water washing process and then dried by dry superheated steam circulated in a closed loop past the textiles. Part of the steam in the circulation loop is diverted and heated by being compressed to a temperature exceeding 100xc2x0 C. and then lead to a heat exchanger, where the heat released during the condensing process is transferred to the steam in the circulation loop.
The objective is also achieved by a method for washing and drying textiles in a treatment chamber where the textiles are first treated in a water washing process and then dried by dry superheated steam circulated in a closed loop past the textiles. Part of steam in the circulation loop is diverted and heated by being compressed to a temperature exceeding 100xc2x0 C. and then led to a heat exchanger, where heat released during the condensing process is transferred to the steam in the circulation loop.
In one embodiment of the invention, in which dry superheated steam is used as the drying medium during the drying process and, further, compressor means are provided for compressing the steam discharged from the machine and lead it to condenser means provided to return to the process heat released during the condensing process, the advantage is obtained that the dehumidification of the textile garments takes place in a more efficient way so that the drying time can be considerably shortened. Due to the fact that the steam transfers heat to the fibres of the textile garments in a more efficient and careful way, as a result also the tendency of creasing is reduced and the relatively small volume of the washing drum of the machine can be accepted. In addition, the full wash load can be dried in one and the same drying process instead of in two batches as up to now. Bythe invention possibilities are opened up of drying wool garments which has not been considered possible in the past due to the great risk of crease. In using steam as the drying medium this risk is considerably reduced and as the drying process only requires moderate drying medium flows and, in addition, the steam well penetrates the fibres of the wool garments without any stirring of the garments by tumbling the drying process becomes very careful.